This is really cool. You can create a photo collage of all your friends on facebook by doing the following:
1) Login to facebook and go to the Friends tab.
2) Under the Show drop-down menu, select --- as in the picture below.

3) Now you can do a Printscreen and paste in any photo-editor. Alternatively, you can use a screen capture tool like
SnagIt. 

Good luck!
Faisal Laljee